The government has ruled out proposals to build a major airport in the Thames Estuary or Kent to increase flight capacity for London.
The Prime Minister told the House of Commons the government had no plans to construct a new airport in the area.
Mr Cameron was responding to a question by Gillingham and Rainham Conservative MP Rehman Chishti.
Mayor of London Boris Johnson has been considering plans for a new airport in Kent and the Thames Estuary.
Mr Johnson wants to increase flight capacity around London without expanding Heathrow.
Several options have been examined including the construction of an airport at Cliffe, on the Hoo peninsula.
The area in north Kent is home to thousands of migratory birds.
The RSPB, Medway Council and Kent County Council had previously said the plan would "devastate the environment".
Mr Cameron told the House of Commons on Wednesday: "The Department for Transport has no plans to build an airport in the Thames Estuary, Medway or Kent.
"We have also scrapped plans to build a third runway at Heathrow."
A spokeswoman for the Mayor of London said the mayor had kickstarted a debate about the best way to increase airport capacity in and around London.
She added: "Whatever conclusion is eventually reached it is vital that a location for extra runway capacity is found for London to remain one of the leading world cities."
Following Mr Cameron's comments, Mr Chisti said: "I am delighted by the Prime Minister's response and hope this will put an end to any further speculation."